I bought an SCT custom chip from JMS Chip that is set up to work with the mods listed in my sig. They bumped the timing 2 degrees and leaned out the A/F 3% and WOT. After I installed it I noticed some detonation in 3rd and 4th gear under hard accelerating. After filling up with fresh 93 octane and Octane booster, I ran the car again. This time the detonation was worse(80 degree weather) so I removed the chip and the detonation was gone. I called JMS and they told me that the tune may have been a little aggressive and to send it back for them to pull a 1.5 degrees of timing. With the chip removed, I filled up with 87 octane and the detonation is back but not nearly as bad. So, does this mean my car is running lean because of my mods, and since the chip leaned it out even more the detonation was worse? I am wondering because if they just pull timing but leave the car lean I don't think the detonation will go away. Thanks for any advice.